fix(lsp): apply each rename edit to its own document

Assisted-by: GLM 5.3 Flash

CHANGELOG.md

@@ -11,6 +11,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 -
 
+### Fixed
+
+- **Rename edits land in their own documents.**  A rename collected the
+  ranges of every reference across the open documents but applied them all
+  to the document that started it, so renaming a symbol used in a second
+  file moved that file's text into the first.  Each edit now applies to the
+  document it was collected in.
+
 ## [0.35.0] - 2026-09-22
 
 ### Added

lsp/handlers.go

@@ -229,7 +229,9 @@ func (s *Server) references(p referenceParams) []Location {
 	return out
 }
 
-// rename renames a label across the document.
+// rename renames a label across every document the references reach.  Each
+// edit is grouped under the URI it belongs to: a range collected in another
+// file must never be applied to the document that started the rename.
 func (s *Server) rename(p renameParams) *WorkspaceEdit {
 	text := s.docs[p.TextDocument.URI]
 	word, _ := wordAt(text, p.Position)
@@ -244,13 +246,11 @@ func (s *Server) rename(p renameParams) *WorkspaceEdit {
 	if len(refs) == 0 {
 		return nil
 	}
-	edits := make([]TextEdit, 0, len(refs))
+	edits := make(map[string][]TextEdit, len(refs))
 	for _, loc := range refs {
-		edits = append(edits, TextEdit{Range: loc.Range, NewText: p.NewName})
-	}
-	return &WorkspaceEdit{
-		Changes: map[string][]TextEdit{p.TextDocument.URI: edits},
+		edits[loc.URI] = append(edits[loc.URI], TextEdit{Range: loc.Range, NewText: p.NewName})
 	}
+	return &WorkspaceEdit{Changes: edits}
 }
 
 // documentFormatting returns a single edit that replaces the whole document

lsp/server_test.go

@@ -1074,3 +1074,49 @@ func TestCrossFileDefinitionAndReferences(t *testing.T) {
 		t.Errorf("references by uri = %v, want one in each file", byURI)
 	}
 }
+
+// TestRenameGroupsEditsByDocument pins the grouping contract: every edit is
+// applied to the document it was collected in, so a cross-file rename never
+// corrupts the origin buffer.
+func TestRenameGroupsEditsByDocument(t *testing.T) {
+	docA := "TEXT \u00b7caller(SB), NOSPLIT, $0\n" +
+		"\tCALL \u00b7helper(SB)\n" +
+		"\tRET\n"
+	docB := "TEXT \u00b7helper(SB), NOSPLIT, $0\n" +
+		"\tRET\n"
+	uriA := "file:///rename_a_amd64.s"
+	uriB := "file:///rename_b_amd64.s"
+	in := frame(1, "initialize", map[string]any{}) +
+		frame(nil, "initialized", map[string]any{}) +
+		frame(nil, "textDocument/didOpen", map[string]any{
+			"textDocument": map[string]any{"uri": uriA, "languageId": "gasm", "version": 1, "text": docA},
+		}) +
+		frame(nil, "textDocument/didOpen", map[string]any{
+			"textDocument": map[string]any{"uri": uriB, "languageId": "gasm", "version": 1, "text": docB},
+		}) +
+		frame(2, "textDocument/rename", map[string]any{
+			"textDocument": map[string]any{"uri": uriA},
+			"position":     map[string]any{"line": 1, "character": 8}, // on helper in CALL ·helper(SB)
+			"newName":      "renamed",
+		}) + frame(nil, "exit", nil)
+	msgs := run(t, in)
+	resp := findByID(msgs, 2)
+	if resp == nil {
+		t.Fatal("no rename response")
+	}
+	var edit WorkspaceEdit
+	if err := json.Unmarshal(mustResult(t, resp), &edit); err != nil {
+		t.Fatal(err)
+	}
+	if len(edit.Changes[uriA]) != 1 || len(edit.Changes[uriB]) != 1 {
+		t.Fatalf("edits per uri = %d and %d, want one each", len(edit.Changes[uriA]), len(edit.Changes[uriB]))
+	}
+	gotA := applyEdits(docA, edit.Changes[uriA])
+	gotB := applyEdits(docB, edit.Changes[uriB])
+	if !strings.Contains(gotA, "CALL renamed(SB)") || strings.Contains(gotA, "renamed(SB), NOSPLIT") {
+		t.Errorf("caller document rename wrong: %q", gotA)
+	}
+	if !strings.Contains(gotB, "TEXT renamed(SB)") {
+		t.Errorf("helper document rename wrong: %q", gotB)
+	}
+}